Conventional antenna towers include a single vertical mast on the order of several hundred feet, on which one or more antenna elements are mounted. The single vertical mast is anchored by a footer of reinforced concrete and one or more guy wires attached to the mast at varying vertical heights and anchored to guy wire footers disposed radially around the base of the antenna. The antenna elements are electrically coupled to one or more transceivers, which are located proximate to the antenna masts' base, or remotely.
Antenna mast sections are typically arranged as three long, narrow, planar, rectangular members connected to one another at approximately 60 degrees to form a triangular cross section. Each long, narrow, planar, rectangular is defined by two long parallel beams mutually connected by angled braces. This conventional antenna tower configuration yields an acceptably rigid tower with a minimal amount of material, but requires stabilization by guy wires having a relatively wide footprint, i.e., having guy wire anchors that are disposed relatively far from the mast itself. Where shorter antenna heights are acceptable, conventional antenna towers are constructed as free standing assemblies with a square cross sections that taper from a wide base to a relatively narrow top. In these cases, the tower typically has four footers anchoring each corner of the tower, and guy wires are unnecessary. FIG. 1 shows two examples of prior art antenna towers.
FIG. 1(a) shows a single-mast type conventional antenna tower. The conventional single mast tower of antenna of FIG. 1(a) includes a footer 105 that anchors the antenna mast. One or more mast sections 110 are mutually vertically connected and anchored to footer 105. Mast sections 110 are conventionally triangular or rectangular in cross section and formed of a plurality of vertically arranged beams 112 with angled cross braces 114. The antenna tower of FIG. 1(a) includes one or more antenna elements 115. Antenna elements 115 are electrically coupled to a transmitter, receiver, or transceiver by a cable, not shown. The antenna tower of FIG. 1(a) also conventionally includes lightning arresting structures and aircraft warning lamps, not shown. The antenna tower of FIG. 1(a) includes one or more guy wires 120 that provide lateral stability to the antenna and are anchored to guy wire footers, not shown.
FIG. 1(b) shows a conventional free standing antenna tower. The antenna tower of FIG. 1(b) includes a plurality of footers 130, typically disposed at the four corners of the antenna tower. The antenna tower of FIG. 1(b) is constructed of a plurality of tapering mast sections 135, each of which has a rectangular cross section and is formed of a plurality of substantially vertical but non-parallel beams 132, mutually connected by a plurality of cross braces 134. The antenna tower of FIG. 1(b) includes one or more antenna elements 140. Antenna elements 140 are electrically coupled to a transmitter, receiver, or transceiver by a cable, not shown. The antenna tower of FIG. 1(b) also conventionally includes lightning arresting structures and aircraft warning lamps, not shown.
Conventionally, single mast antenna towers are raised in phases by sequentially installing relatively short mast sections, which are sequentially anchored to guy lines as they are put into place. Typically, the antennal mast footer is poured. Next, a mast section is installed into the footer, typically with the assistance of a mobile crane. Successive mast sections are then attached to the previous mast sections and are periodically secured with radial connections to guy wires anchored to pre-poured guy wire footers until the desired height is achieved. Antenna elements, electrical signal cables to the antenna elements, lighting arresting devices, and aircraft warming lamps are typically installed last, or are pre-installed on the appropriate mast sections prior to the mast sections being installed on the tower.
Conventional antenna tower assemblies are poorly suited for remote installation locations, which are characterized by a number of challenging factors. First, remote installation locations tend to be difficult to access by road, which limits the options available for transporting material to the site. Material and manpower for remote tower construction often must be transported by air, or even by beasts of burden in extreme cases. When there is road access, the quality of the roads often limits them to light vehicles, jeeps, HUMVEES, light trucks, etc., which eliminates the possibility of using most mobile cranes for assembly. Additionally, the work site is generally small, e.g., a rocky outcropping on top of a hill, so the number of workers that can be on-site to assist in tower assembly is small.
Remote worksites pose other unique challenges as well. For example, the soil may be extremely shallow and/or rocky, which makes conventional installation of guy wire footings, which require poured concrete to a depth of several feet, difficult or impossible. The difficulty of installing conventional footings has two disadvantageous impacts. First, without conventional footings achieving the necessary mechanical strength of a guy wire anchor is difficult. Second, conventional towers are usually grounded through guy wire footings, i.e., the conductive paths from lighting arrestors are directed through the footings and into the ground. Without the ability to install a conventional footing, the problem remains regarding how to direct the current associated with lighting strikes.
Additionally, remote sites, such as rocky promontories are generally poorly suited for conventional placement of guy wire supports. This is so because conventional guy wire installation requires a relatively large flat area around an antenna to anchor the guy wires. Such as large flat area is not available if a structure such as an antenna tower is to be installed on a rocky promontory.